There has been known a conventional electric steering lock device disclosed in the Japanese Patent brochure of Patent Application Laid-Open No. 2005-214118 (Patent Document 1). As shown in FIG. 14, the conventional electric steering lock device 100 of this type includes: a lock member 102 configured to be displaced between a locking position for prohibiting rotation of a steering shaft 101 and an unlocking position for permitting rotation of the steering shaft; a first switch SW1 configured to detect that the steering shaft 101 is locked; a second switch SW2 configured to detect that the steering shaft 10 is unlocked; and a CPU 103 that is an electric steering lock controller configured to determine a position of the lock member, based on detection outputs from the first detection switch SW1 and the second detection switch SW2, and thus to control driving of the lock member 102. Meanwhile, lock and unlock information from the CPU 103 and the detection output from the second detection switch SW2 are supplied to a starter control device 104 that is a vehicle-side controller. The starter control device 104 determines the locked state and the unlocked state of the steering shaft 101 based on these input states. Moreover, the starting and the like of the engine are performed based on an engine start instruction, only when the steering shaft 101 is in the unlocked state. The engine is not started, even if the engine start instruction is given, when the steering shaft 101 is located in the locked position.
Incidentally, in the electric steering lock device 100, it is necessary to surely avoid such a situation that the starter control device 104 starts the engine in accordance with erroneous information being outputted to the starter control device 104 and indicating that the steering shaft 101 is located in the unlocked position in spite of the fact that the steering shaft 101 is actually located in the locked position.
In the above conventional example, the output from the second detection switch SW2 and the output from the CPU 103 are supplied to the starter control device 104. Therefore, when unlock information is erroneously outputted due to a failure of the second detection switch SW2 though the steering shaft 101 is actually located in the locked position, it is possible to determine that there is the failure of the electric steering lock device 100 by use of lock information from the CPU 103. Meanwhile, when the unlocked state is erroneously detected due to runaway or the like of the CPU 103 though the steering shaft 101 is actually located in the locked position, it is possible to determine that there is the failure of the electric steering lock device 100 by use of lock information (information of not being located in the unlocked position, to be accurate) from the second detection switch SW2.
However, it is impossible to determine the failure of the electric steering lock device 100 when the output information from both the second detection switch SW2 and the CPU 103 to the starter control device 104 is the erroneous information (the erroneous information indicating that the steering shaft 101 is located in the locked position) at the same time. Specifically, there is a problem that determining the failure of the electric steering lock device 100 is impossible when the failure of the second detection switch SW2 and the runaway or the like of the CPU 103 occur at the same time.
To solve this problem, an electric steering lock device shown in FIG. 15 and FIG. 16 is conceivable. The electric steering lock device 110 includes: a lock member configured to be displaced between a locking position for prohibiting rotation of a steering shaft and an unlocking position for permitting rotation of the steering shaft; a first detection switch SW1 configured to detect that the steering shaft is locked; second, third and fourth detection switches SW2, SW3 and SW4 configured to detect that the steering shaft is unlocked; and an electric steering lock controller 111 configured to determine a position of the lock member, based on detection outputs from the first detection switch SW1 and the second detection switch SW2, and thus to control driving of the lock member. Lock and unlock information of the electric steering lock controller 111 and detection outputs from the third detection switch SW3 and the fourth detection switch SW4 are outputted to a vehicle-side controller (not shown).
With this configuration, it is possible to determine a failure of the electric steering lock device 110, even if a failure on either the third detection switch SW3 or the fourth detection switch SW4 for detecting the unlocked position and runaway or the like of the electric steering lock controller 111 occur at the same time. Specifically, the vehicle-side controller acquires the locked position information (of not being located in the unlocked position, to be accurate) from the unbroken switch out of the third detection switch SW3 and the fourth switch SW4 so that a determination can be made that there is a failure in the electric steering lock device 110. For example, even if the electric steering lock controller 111 outputs erroneous information of being located in the unlocked position though the steering shaft is actually located in the locked position and the third detection switch SW3 outputs an L signal (indicated with a broken line in FIG. 16) due to a failure, it is possible to determine the failure of the electric steering lock controller 111 and the third detection switch because the fourth detection switch SW4 outputs an H signal.
However, there is a problem of increase in cost and size of the electric steering lock device 110 because it is necessary to provide the electric steering lock device 110 with the four switches SW1 to SW4.
Accordingly, the present invention has been made to solve the above-described problem and an object thereof is to provide an electric steering lock device that is capable of outputting a signal to enable determination of failures even if a failure on a detecting module side and a failure on a control side occur at the same time, and also capable of reducing the number of detecting module.